The net magnetic force acting on the loop is the superposition of the forces on each side of the loop. The forces on the two sides perpendicular to the long straight wire will cancel (right hand rule). The magnitude of the magnetic force between two wires with currents I_1 = 12 A and I_2 = 5 A of length L = 0.5 m ( assuming not given in question).
so the forces on the near and far wires are
The force F_n is an attractive one, while F_f is a repulsive one (right hand rule). The magnitude of the force is therefore
Applying the work-energy theorem, if we can neglect the friction between truck and road, the total change in kinetic energy must be equal to the work done by the external forces.
This work, is just 4,475 J.
So we can write the following equation:
where m= mass of the truck = 2.5*10³ kg.
So, we can find the speed v, as follows:
b)
The work done by the man, is just the horizontal force applied, times the displacement produced by the force horizontally: